1. Field of the Invention
The present invention relates generally to packaging of opto-electronic components, and more particularly to packaging of an image sensor.
2. Description of Related Art
Image sensors and image sensor assemblies are best known as components in modern consumer goods such as hand-held cameras. In these assemblies, an image sensor is mounted inside a housing, with the housing providing support for a window. Visible light passes through the window and strikes the image sensor.
In assembly, an underside of the image sensor is mounted to a printed circuit board. Then the housing is mounted to the printed circuit board around the image sensor. The housing not only provides a hermetic barrier around the image sensor, but also a top opening above the image sensor for installation of the window thereat.
The image sensor is highly sensitive to dust, contamination, moisture and other environmental factors. The image sensor has an active area which is responsive to light. Even the slightest blemish on the active area is liable to distort or obstruct light passing therethrough, resulting in defective operation or failure of the image sensor assembly. Thus the provision of a hermetic space for the image sensor is critical.
In a conventional image sensor assembly, the opening of the housing above the image sensor is hermetically sealed with plate glass to provide the window and the hermetic space containing the image sensor. The window allows light to pass therethrough into the housing.
As the art of opto-electronics progresses toward smaller lightweight electronic devices, it is becoming increasingly important that the size of image sensor assemblies used in these electronic devices is correspondingly small. A device such as a camera employs an optical lens that focuses visible light into the image sensor package. The optical lens has a focal length F, which limits how close the optical lens can be placed in relation to the image sensor. This necessarily makes the camera rather bulky.